Method for removing oil fat and grease from water

ABSTRACT

Free oil, fat and grease contaminate water and wastewater these contaminants can be removed by an efficient separator system and allow the contaminants to be recovered at their maximum concentration.

FIELD OF THE NVETION

The invention relates to a method of removing free oil, fat and greasefrom a continuous flow of water or similar liquid, the system allows thefree oil, fat and grease to be separated in an efficient manner within achamber, the separated free oil, fat and grease is then removed inconcentrated form from the top of the chamber whilst water withsignificantly reduced free oil, fat and grease is allowed to exist fromthe bottom of the chamber via an external level control device.

BACKGROUND OF THE INVENTION

Most industries face significant problems with processing and disposalof liquid waste that is contaminated with free oil, fat and grease. Thistype of waste posses a major threat to the global environment and thereis a need for simple and cost effective solution to remove thesecontaminants to allow clean water discharge to public sewer, wastetreatment plants, inland waterways and seas or oceans.

BRIEF DISCUSSION OF THE INVENTION

The invention relates to a vertical cylindrical vessel into which areplaced a series of cylinders some with end plates and some without thatform a series of vertical annulus flow areas, this arrangement allowsthe liquid which is contaminated with free oil, fat and grease to flowin upwards or downwards directions through the annulus areas. This flowwhich takes place at ultra low velocity allows the free oil, fat andgrease to coalesce and rise vertically and separate out until a freeoil, fat and grease layer is formed at the top of the vertical cylinderwhere it can be removed via an overflow outlet. The water phase whichhas now been de-contaminated is allowed to discharge from the bottomoutlet of cylindrical vessel. An external level control device is fittedto enable variable control of the water/free oil, fat and grease levelswithin the vertical cylindrical vessel.

DETAILED DESCRIPTION OF THE INVENTION

Refer Drawing FIG. 1

A liquid such as water which is contaminated by free oil, fat or greaseis supplied to the Counter-flow separator by a non-emulsifying pump atinlet (1) the oily water rises through a centrally located inlet pipe(2) which is sized to suit the required flow rate. The oily water onreaching the outlet point of the vertical riser pipe separates into twostreams, one of these streams is of large oil droplets that impinge onthe baffle plate (3) which is of an invert cone shape and is supportedby one or more pillars to the top section of sleeve (16). These largeoil droplets which have a specific-gravity less than that of the watercarrier fluid coalesces on the underside of the inverted cone (3) andrise to float on the surface of the carrier fluid, in this case water,to form an oil layer at (4) free oil zone, in the mean time the carrierfluid water which also contains finer oil droplets of varying size ismade to move in a downward direction through the annulus chamber createdby the outer body (17) and inner sleeve (16).

The velocity of this downward movement between outer body (17) andsleeve (16) is such that remaining larger-oil droplets being a lighterspecific gravity than the carrier fluid water coalesces together andinvert and begin to move up against the downward flow of the carrierfluid water, thus further separation takes place in chamber (5).

The larger oil droplets that have coalesced together and are risingeventually merge with the previously separated oil at (4) free oil zone.

Carrier fluid water with finer oil droplets that are being carried in adownward direction reach the bottom of the annulus chamber (5) and areturned in an upward direction into annulus chamber (7) between sleeve(16) and sleeve (18), here the finer oil droplets are rising with thecarrier fluid water and these finer oil droplets coalesce on theirvertical movement through annulus area (7) to form larger oil droplets.

These larger oil droplets impinge on baffle plate (8) at the top ofannulus chamber (7) and due to the difference in specific gravitybetween the oil and the carrier fluid water the Small-coalesced oildroplets rise vertically through one or more outlet pipes (9) and upinto the oil collection area (4) free oil zone.

Carrier fluid water which is now more or less oil free moves intoannulus area (10) between sleeve (18) and the outside of the inlet pipe(2) and moves in a downward direction.

A small quantity of air (20) is introduced via a connection (19) and asparge pipe (21) at the bottom of annulus area (10) this air rises andadheres to any fine oil droplets that may be carried in a downwarddirection through annulus area (10) and separates any remaining veryfine oil droplets from the carrier fluid water.

The fine oil droplets are carried by the air vertically to the top ofannulus (10) where the oil coalesces with other larger droplets onimpingement plate (8) and the air and coalesced oil droplets risethrough one or more pipes (9) into the oil collection zone (4) free oilzone.

Carrier fluid water which is more or less free of oil and is existingfrom annulus chamber (10) moves downwards into exit chamber (11) and onthrough the outlet pipe (12), this pipe can be adjusted in a verticalmovement up or down to permit the level of free oil in zone (4) to bemaintained until such time as the level of free oil rises on top of thecarrier fluid water to allow the free oil to exit at the oil outletconnection (13).

Provision is made to allow any solid material that may accumulate in theoutlet chamber (11) to be removed through outlet (14).

1. A continuous flow separator for removing oil, fat, grease and thelike from waste water comprising: a vertical cylindrical vessel having acentrally located waste water inlet at its base, a vertical riser pipelocated centrally within the vessel and in fluid communication with theinlet and having an opening at its top, a first baffle located withinthe vessel and above the riser pipe, a free oil zone located between thetop of the riser pipe and the oil outlet pipe, a first oil outlet piperemoving oil from the free oil zone, a first annulus chamber formedbetween the riser tube and a first sleeve surrounding the riser tube influid communication with the free oil zone, a second annulus chamberformed between a second sleeve surrounding the first sleeve and the topof which is in fluid communication with the top of the first annuluschamber, a third annulus chamber formed between the second sleeve and anouter wall of the cylindrical vessel and the bottom of which is in fluidcommunication with the second annulus chamber, a second baffle platelocated above the first and second sleeves and separating the first andsecond annulus chambers from the free oil zone, at least one second oiloutlet pipe for removing oil from the top of the second first and secondannulus chambers, an air inlet connected to a sparge pipe located at thebottom of the first annulus chamber, and a waste water outlet located atthe bottom of the first annulus chamber.
 2. A continuous flow separatoras defined in claim 1 further comprising a pump to supply waste water tothe waste water inlet.
 3. A continuous flow separator as defined inclaim 2 wherein said pump is a non-emulsifying pump.
 4. A continuousflow separator as defined in claim 1 wherein said first baffle plate hasan inverted cone shape.
 5. A continuous flow separator as defined inclaim 1 wherein said outlet pipe can be adjusted in a vertical directionto control the level of liquid within the vessel.
 6. A continuous flowseparator as defined in claim 1 wherein the outlet chamber has a solidwaste outlet to permit the removal of solids which may accumulate in theoutlet chamber.